Synergistic Effect of Charge-Modulated Molecular Passivation in MA/Br-Free Perovskite Solar Cells

Molecular passivation represents a promising avenue for enhancing both the efficiency and operational stability of perovskite solar cells. This work reports on the effect of diammonium iodide functional molecules featuring aryl or alkyl cores onto 3D-perovskite surfaces. Our findings reveal the remarkable efficacy of piperazine dihydriodide, characterized by an alkyl core and electron-rich -NH terminal, in mitigating surface and bulk defects while modifying surface chemistry and improving carrier extraction efficiency. This results in an impressive efficiency of 23.17% (1 cm² area) with superior long-term stability. Device analysis substantiates that these robust bonding interactions reduce defect densities in the perovskite film and suppress ion migration. This report will shed light on the synergetic effect of bifunctional molecules in defect mitigation, opening avenues for design strategies centered on bonding-regulated molecular passivation to enhance solar cell performance and stability.